A purpose of a brush in an electrical device is to pass electrical current from a stationary contact to a moving contact surface, or vice versa. Brushes and brush holders may be used in electrical devices such as electrical generators, electrical motors, and/or slip ring assemblies. Brushes in many electrical devices are blocks or other structures made of conductive material, such as graphite, carbon graphite, electrographite, metal graphite, or the like, that are adapted for contact with a conductive surface or surfaces to pass electrical current.
In some designs, a brush box type brush holder, or other type of brush holder, may be used to support a brush in contact with a moving contact surface of an electrical device during operation. The brush and brush box may be designed such that the brush can slide within the brush box to provide for continuing contact between the brush and the moving contact surface contacted by the brush. During operation an anomalous and/or threshold condition may occur, which may be indicative that one or more components of the electrical device may need to be replaced, one or more components of the electrical device may require inspection or attention, and/or maintenance may need to be performed. It would be advantageous to monitor one or more components of an electrical device in order to observe the occurrence of an anomalous and/or threshold condition.
For smooth operation of an electrical machine with brushes such as these, it is desirable to monitor the brushes continuously when in operation, in particular to measure not only the brush wear, but also other parameters of the electrical power train, such as rotation speed, temperature, out-of-roundness, estimated brush life, slip ring behavior, and the like. Existing systems available on the market for remote monitoring, monitor the brush wear only and include a micro switch, optical switch (see for example GB2172445), a magnetic reed switch, see for example GB2092390, SU860187, and US2009/0206695 all comprising a magnetic reed switch at the perimeter and base of the brush holder that in cooperation with a magnetic material inside the brush will generate a signal when the brush is almost worn. Other systems are based on a wire inside the brush that makes contact at the end of life of the brush. Rather than indicating only a good or bad condition of a device part like the wear of a brush or slip ring, it is also desirable to predict a possible failure or defect before any real damage is done, based on the measurement results. Examples are sudden increased brush wear, a change in slip ring out-of-roundness, temperature rise of brush box, los of contact of the brushes with the slip ring, changes in rotation speed, changes in currents trough the brushes, etc. Wear of the slip ring can normally only be detected with measurements done during maintenance, which requires stopping and making the machine safe. Wear of the slip ring will also lead to increased wear of the brush. This can cause a lot of conductive dust (carbon) which holds risks for short circuits or other problems.
The measurement data should be preferable collected on a central server, for example on internet, such that the owner or technician of the device can follow from anywhere the status in real time and alerts can be send using modern communication techniques like e-mail, SMS etc. Also history data should be preferable available to compare measurement data. It is accordingly an object of the present invention to enable a continuous and remote monitoring of the overall performance of an electrical power train (electrical generator/electrical motor).